Methods for improving a phenol extraction process



March 17, 1970 R. L. MENZL ET AL 3,501,399

METHODS FOR IMPROVING A PHENOL EXTRACTION PROCESS Filed May 29; 1968 2Sheets-Sheet 1 Final Raffinafe v Phenol 1st. CONTACTING ZONE- 4Disfg'l/afe Extract 2nd. CONTACTING ZONE Final Distillate Raff/note Exfracf PI; 00/

INVENTORS. Roland L. Menz/ reder/ck M. .Sc/wess/er Lowell 71 Dadds By awATTORNEY Marbh 17, 1970 R. L. MENZL ETAL METHODS FOR IMPROVING A PHENOLEXTRACTION PROCESS Filed May 29, 1968 2 Sheets-Sheet 2 mZON QZFOFFZOO uN uZON 23mm uwmDw km INVENTORS. Roland L. Menz/ Freda/ck n. Sc/auess/erLowell 71 Dodds ATTORNEY 3 3st QQ United States Patent Ofi ice 3,501,399Patented Mar. 17, 1970 3,501,399 METHODS FOR IMPROVING A PHENOLEXTRACTION PROCESS Roland L. Menzl, Hammond, Ind., Frederick W.Schuessler, Chicago, Ill., and Lowell T. Bodds, Lake Village, Ind.,assignors to Standard Oil Company, Chicago, 111., a corporation ofIndiana Filed May 29, 1968, Ser. No. 733,166

Int. Cl. Cg 21/00 US. Cl. 208317 12 Claims ABSTRACT OF THE DISCLOSUREThese methods improve the operation of a phenol extraction processhaving two parallel contacting zones of unequal capacities. The methodfor improving the efficiency of the process comprises connecting twocontacting zones in series with the existing two contacting zones. Themethod for improving the capacity and the etficiency of the processcomprises connecting two contacting zones in series with the existingtwo contacting zones and employing interstage cooling.

BACKGROUND OF THE INVENTION Lubricating oil fractions can be obtainedfrom a pctroleum crude oil. Such fractions contain not only the desiredhigh viscosity index hydrocarbons, isoparai'lins and cyclic compoundswith long parafiinic side chains, but also undesirable highly condensedcyclic compounds of low viscosity index, polycyclics with no or onlyshort side chains, and heterocyclics which reduce the oils stability.The undesirable constituents are selectively removed from the oil bymeans of solvent extraction processes. These solvent extractionprocesses include the furfural, phenol, Duo-Sol, Edeleanu, Chlorex, andnitrobenzene processes.

Fundamentally, all of the above-mentioned processes are similar. Ineach, the oil is contacted with a selective solvent that extracts theundesirable components and, subsequently, the solvent is separated fromthe extract and raflinate streams. The solvent causes the hydrocar-'b0r1 stream to separate into two phases, a first phase consistingprimarily of solvent in which are dissolved the extracted objectionablebodies, such as polycyclic aromatics, and a second phase consisting ofthe refined oil saturated with the solvent. The primary purpose of theseprocesses is to improve the quality of the lubricating oil distillatebeing treated by selectively removing the undesirable componentstherefrom, thereby improving the viscosity index and ability to resistoxidation of the distillate. Such separation of lubricating oilhydrocarbons is entirely physical. The yields of such a process varywith the efficiency of the solvent and the efficiency of the processitself. Efficiency is defined as the barrels of refined oil obtained perbarrel of solvent charged to the extractors. This is a suitabledefinition, since the quantity of solvent used in the process has alarge effect on the economics of the process. The cost of solventrecovery is high. Yield is defined as the barrels of refined oilobtained per barrel of distillate charged to the extractors.

A suitable solvent extraction process for the treating of lubricatingoil distillates is the process that employs phenol as the solvent. Insuch a process, countercurrent contactors may be connected in series andan increase in the number of countercurrent contacting stages reducessolvent requirement and improves the selectivity of the process.

' One phenol extraction process that has been in commercial operationcomprises two parallel contacting zones of unequal capacity. In thisprocess, a lubricating oil fraction is treated to improve its color, itsability to resist oxidation, and its viscosity index. The lubricatingoil fraction is introduced into the two parallel contacting zones, afirst contacting zone and a second contacting zone. A first phenolstream is introduced into the first contacting zone and is passedtherethrough countercurrently to the lubricating oil fraction. A secondphenol stream is introduced into the second contacting zone and ispassed therethrough countercurrently to the lubricating oil fraction. Afirst raflinate efiluent and a first extract etfiuent are withdrawn fromthe first contact-zone while a second raffinate efiluent and a secondextract effluent are withdrawn from the second contacting zone. Thefirst raffinate effluent and the second rafiinate effiuent comprise theimproved lubricating oil distillate and make up the usable product ofthis process.

Now there have been found a method for increasing the efiiciency and amethod for increasing the capacity and the efiiciency of this phenolextraction process wherein the amount of solvent required per barrel oflubricating oil fraction charged is reduced and the yield of usableproduct is increased.

SUMMARY OF THE INVENTION Briefly, in accordance with the presentinvention, there is a method for increasing the efficiency of a processfor treating a lubricating oil distillate to improve the color, theability to resist oxidation, and the viscosity index of the distillate.The process to which this method is applicable comprises introducing afirst phenol stream into a first contacting zone, passing said firstphenol stream through said first contacting zone countercurrently to afirst distillate stream, introducing a second phenol stream into asecond contacting zone, said first contacting zone and said secondcontacting zone being parallel and being of unequal capacities, passingsaid second phenol stream through said second contacting zonecountercurrently to a second distillate stream, said first distillatestream and said second distillate stream being charged to said firstcontacting zone and said second contacting zone, respectively,withdrawing from said first contacting zone a first extract efliuent anda first rafiinate efi'iluent, and withdrawing from said secondcontacting zone a second extract efiiuent and a second rafiinateeflluent. The method for increasing the capacity of this processcomprises: Combining the first extract eifiuent and the second extractefiiuent and to form an intermediate-extract efiiuent; passing saidintermediate-extract efiluent into and through an intermediate-extractsurge drum; withdrawing said intermediate-extract efiiuent from saidintermediateextract surge drum; dividing said intermediate-extractefiluent .into a first intermediate-extract stream and a secondintermediate-extract stream; passing said first intermediate-extractstream into and through a third contacting zone; introducing into saidthird contacting zone a third distillate stream, said third distillatestream being passed through said third contacting zone countercurrentlyto said first intermediate-extract stream; withdrawing from said thirdcontacting zone a first finalextract stream and a firstintermediate-raflinate stream; passing said second intermediate-extractstream into and through a fourth contacting zone; introducing into saidraifinate stream into a thirdintermediate-raffinate stream and a fourthintermediate-raffimate stream; combining said firstintermediate-Iafiinate stream with said third intermediate-raflinatestream to form a fifth intermediaterafiinate stream; passing said fifthintermediate-raffinate stream into said first contacting zone, saidfifth intermediate-raffinate stream being said first distillate. streamthat is introduced into said first contacting zone; withdrawing as afirst final-raffinate stream from said first contacting zone said firstraftinate effiuent; passing said fourth intermediate-raffinate streaminto and through said second contacting zone, said fourthintermediateraflinate stream being said second distillate stream that isintroduced into said second contacting zone; withdrawing as a secondfinal-raffinate stream from said second contacting zone said secondraffinate efiluent.

In this method, the third contacting zone and the fourth contacting zonemay be of equal capacities. The first intermediate-extract stream andthe second intermediateextract stream may be equal in volume. The firstcontacting zone may be a gravimetric extractor, and the secondcontacting zone may be a centrifugal extractor.

Also, in accordance with the present invention, there is a method forincreasing the capacity and the efficiency of the process. This methodcomprises the above-defined method and, in addition, cools theintermediate-raffinate material that is to be introduced into the firstcontacting zone to a temperature that is about F. to about F. lower thanthe temperature of the first phenol stream being introduced into thefirst contacting zone. Therefore, the first intermediate-raflinatestream may be passed through a cooler to cool the fifthintermediate-.rafifiuate stream to a temperature that is about 10 F. to25 F. lower than the temperature of the first phenol stream beingcharged to the first contacting zone. As an alternative, the fifthintermediate-Iaflinate stream may be passed through the cooler.

DESCRIPTION OF THE DRAWINGS Two figures are presented herewith tofacilitate better understanding of the present invention. FIGURE 1 is asimplified schematic drawing of the process for treating lubricating oildistillates to which the present invention is applicable. Two parallelcontacting zones are employed in this process.

FIGURE 2 is a simplified schematic representation of the same processdepicted in FIGURE 1 after the method of the present invention isemployed.

In these simplified drawings, auxilliary equipment such as pumps,valves, and the like, are not shown. Moreover, the solvent recoveryequipment is not shown. Such items, their use and location are wellknown to those people having ordinary skill in the art. Therefore, theyneed not be represented in the drawings.

Since the efiiciency of a phenol extraction process can be improvedthrough an increase in the number of extraction stages that are used inthe process, contacting zones may be added in series with existingcontacting zones to provide a more efiicient phenol extraction process.

If an existing process for treating lubricating oil fractions comprisestwo parallel contacting zones, into which separate streams of thelubricating oil fraction are introduced and from which separate streamsof raffinate are Withdrawn as improved lubricating oil distillates, theefficiency of this process can be improved by connecting an additionaltwo contacting zones in series therewith. If the existing two contactingzones are of unequal capacity auxilliary equipment such as surge drumsmay be employed to handle the intermediate-raffinate andintermediate-extract streams associated therewith.

Typical lubricating oil fractions that may be treated in a process thatis improved by the method of this invention are petroleum hydrocarbonfractions boiling within the range of about 600 F. to about 1,050 F. atatmos pheric pressure. Such fractions possess a viscosity at 210 F.within the range of about SUS to about 160 SUS.

4 Such hydrocarbon fractions may be either waxy or dewaxed.

The phenol stream may be relatively anhydrous; in such case, water maybe added to the first contacting zone in the phenol extraction system,since water reduces the solvency of the phenol.

In the following examples, which demonstrate the advantageous of thepresent invention, a lube oil distillate having a viscosity of about SUSat 210 F. was employed as the feedstock.

Example I FIGURE 1 represents schematically an actual commercial phenolextraction process. In this particular process, the first contactingzone was an extraction tower and the second contacting zone was acentrifugal contactor. The first contacting zone 11 and the secondcontacting zone 12 were being operated in parallel. Distillate wasintroduced into zone 11 near its bottom by way of line 13. Thisdistillate was maintained at a temperature of about F. and was used at aflow rate of about 250 barrels per hour (b./h.). Phenol was introducedinto zone 11 near its top by way of line 14. This phenol stream wasmaintained at a temperature of about F. and was charged at a flow rateof about 450 b./h. Water was introduced into contacting zone 11 by wayof line 15 at a flow rate of 31 b./h. Final raffinate was withdrawn fromthe top of zone 11 by way of line 16 at a flow rate of about 192 b./h.,while extract was withdrawn from the bottom of zone 11 by way of line 17at a flow rate of about 539 b./h.

Distillate was introduced also into zone 12 by way of line 18. The flowrate of this later distillate stream was about 16 8 b./ h. Phenol wascharged to zone 12 by way of line 19 at a flow rate of about 302 b./ h.Final-raffinate was withdrawn from zone 12 by way of line 20 at a flowrate of about 123 b./h., while extract was withdrawn from zone 12 by wayof line 21 at a flow rate of about 347 b./h.

The total charge of lubricating oil distillate to the above processsystem was about 418 b./h. The total amount of product (raffinate) aftersolvent removal withdrawn from this process scheme was about 282 b./h.The rate of the total amount of phenol charged was 752 b./ h. Therefore,the solvent-to-oil-ratio was 1.8 and the yield, i.e., the ratio ofrafiinate produced to the hydrocarbons charged, was 67.5 volume percent.More-over, the efficiency of this process, as defined above, was about37.5 percent.

Example II An embodiment of the present invention was employed 1 toimprove the efficiency of this above process. The process employing thisembodiment is represented schematically in FIGURE 2. The originalprocess scheme, as presented and numbered in FIGURE 1, is presented onthe right-hand side of FIGURE 2. The lines and equipment presented onthe right-hand side of the dotted line represent the lines and equipmentthat are shown in FIG- URE 1. Therefore, they have the same numbers thatare presented in FIGURE 1. Of course, the quantities of materials andflow rates employed in this scheme are different than those of thecorresponding materials and streams employed in the process depicted inFIGURE 1. The cooler 39, represented by the broken lines, was notemployed in the process of this example and should, therefore, beignored in the discussion of this example.

Phenol was charged to contacting zone 11 by Way of line 14 while a smallamount of Water was charged by way of line 15. The flow rate of phenol,maintained at a temperature of about 174 F., was about 348 b./h. Theflow rate of the water was about 24.6 b./h. Intermediate extract waswithdrawn from zone 11 by way of line 17 at a flow rate of about 439b./h. Phenol as also charged to contacting zone 12 by way of line 19 ata flow rate of about 252 b./ h. and was maintained at a temperature atabout 174 F. Intermediate extract was withdrawn from contacting zone 12by way of line 21 at a flow rate of about 291 b./h. The extract efliuentin line 21 was combined with the extract eflluent in line 17 and thecombined extract eflluent was passed through line 22 intointermediate-extract surge drum 23. This surge drum was necessary, sinceunequal flows of extract were obtained from the two contacting zones.Extract was withdrawn from intermediate-extract surge drum 23 by way ofline 24. This extract stream was then split into two equal streams, oneof which passed through line 25, while the other passed through line 26.The flow rate of the material in line as well as in line 26, was about365 b./h. The extract from line 25 was introduced into contacting zone27, while that from line 26 was introduced into contacting zone 28.

Distillate was charged to contacting zone 27 by way of line 29.Intermediate rafiinate was withdrawn from contacting zone 27 by way ofline 30, while extract was withdrawn from contacting zone 27 by way ofline 31. The distillate was maintained at a temperature of about 163 F.and was introduced into zone 27 at a flow rate of about 187 b./h. Theflow rate of the intermediate rafiinate being withdrawn through line wasabout 204 b./h.

Distillate was also charged to contacting zone 28 by way of line 32. Thedistillate was maintained at a temperature of about 166 F. and was addedat a flow rate of about 187 b./h. Extract was withdrawn from contactingzone 28 by way of line 33, while intermediate raffinate was withdrawnfrom contacting zone 28 by way of line 34. The flow rate of theintermediate-raffinate stream passing through line 34 was about 204 b./h.

The intermediate-rafiinate stream passing through line 30 was introducedinto the intermediate-rafiinate surge drum 35. This surge drum wasemployed to eliminate problems which would arise because of the unequalcapacities of the contacting zones 11 and 12. The intermediaterafiinatestream was withdrawn from surge drum by way of line 36. Thisintermediate-raflinate stream was then divided into two smaller streams,one passing through line 37, while the other passed through line 38. Theflow rate of material passing through line 37 was about 172 b./h'. Theflow rate of material passing through line 38 was about 32 b./h. Theintermediate-raffinate stream in line 34 was passed through line andthen combined with the intermediate-raflinate stream in line 38. Thecombined intermediate-raffinate stream was passed through line 13 intocontacting zone 11 at a flow rate of 236 b./h. Final rafiinate waswithdrawn from the top of contacting zone 11 by way of line 16 at a flowrate of about 137 b./h. The intermediate-raflinate stream passingthrough line 37 was passed through line 18 into contacting zone 12 at aflow rate of about 172 b./h. A final-raffinate stream was withdrawn fromcontacting zone 12 by way of line 20 at a' flow rate of about 133 b./h.The total amount of product (raffinate) after solvent removal withdrawnfrom this process was about 270 b./h.

. The quantities of materials employed in this example indicate that theyield of this process was about 72.2 volume percent. The ratio ofsolvent to oil was about 1.6. The efficiency of this process waspercent. Therefore, it is seen that the use of this embodiment of thepresent invention reduced the required solvent-to-oil ratio from 1.8 to1.6 and increased the efficiency from 37.5 percent to 45 percent.

A preferred embodiment of the present invention to improve the capacityand the efficiency of the process of Example I may be representedschematically by FIGURE 2, if a cooler is placed in line 34 thereof tocool the first intermediate-raflinate stream passing therethrough.Therefore, cooler 39, which is represented by the broken lines, isemployed in and is included in the process scheme of this preferredembodiment.

Phenol was charged to contacting zone 11 by way of line 14 while a smallamount of water was charged to contacting zone 11 by of line 15. Theflow rate of phenol, maintained at a temperature of about 170 F., was417 b./h. The flow rate of the water was about 29 b./h. Intermediateextract was withdrawn from zone 11 by way of line 17 at a flow rate ofabout 503 b./h. Phenol was charged to contacting zone 12 by way of line19 at a flow rate of about 320 b./h. and was maintained at a temperatureof about 170 F. Intermediate extract was withdrawn from contacting zone12 by way of line 21 at a flow rate of about 371 b./h. The extracteffluent in line 21 was combined with the extract eflluent in line 17and the combined extract effluent was passed through line 22 intointermediate-extract surge drum 23. Extract was withdrawn fromintermediate-extract surge drum 23 by way of line 24. This extractstream was then split into two equal streams, one of which passedthrough line 25 while the other passed through line 26. The flow rate ofthe material in line 25, as well as in line 26, was 437 b./h. Theextract from line 25 and the extract from line 26 were introduced intocontacting zones 27 and 28, respectively.

Distillate, maintained at a temperature of about 200 F., was charged tocontacting zone 27 by way of line 29 at a flow rate of about 230 b./h.Intermediate rafiinate was withdrawn from contacting zone 27 via line 30at a fiow rate of about 240 b./h. Extract was withdrawn from contactingzone 27 by way of line 31.

Distillate was also charged to contacting zone 28 by way of line 32.This distillate was maintained at a temperature of about 200 F. and wascharged at a flow rate of about 230 b./h. Intermediate raflinate waswithdrawn from contacting zone 28 by way of line 34 at a flow rate ofabout 240 b./ h. Extract was withdrawn from contacting zone 28 by way ofline 33.

The intermediate-rafiinate stream passing through line 30 was introducedinto and through intermediate-raftinate surge drum 35 and line 36. Theintermediate raffinate was then split into two streams; one passedthrough line 37, while the other passed through line 38. The flow rateof the material in line 37 was 200 b./h. The flow rate of the materialin line 38 was 40 b./h. The intermediateraffinate stream in line 34 waspassed through cooler 39 and line 40. The cooled intermediate-rafiinatestream in line 40 was then combined with the intermediate-rafiinatestream in line 38. The combined intermediate raifinate was passedthrough line 13 into contacting zone 11. The cooler 39 was operated toprovide a temperature for the intermediate raffinate passing throughline 40 that blended with the temperature of the material in line 38 tofurnish a temperature of about F. for the intermediate-raffinatematerial being passed through line 13 into contacting zone 11. Hence,this material being charged into contacting zone 11 had a temperature ofabout 20 F. lower than that of the phenol that was charged to contactingzone 11. This cooled intermediate-raflinate stream was passed throughline 13 at a flow rate of about 280 b./h. Final rafiinate stream waswithdrawn from the top of contacting zone 11 by way of line 16 at a flowrate of about 332 b./h. (10 vol. percent phenol). Theintermediateraflinate stream passing through line 37 was passed throughline 18 into contacting zone 12 at a flow rate of about 200 b./h. Afinal-rafiinate stream was withdrawn from contacting zone 12 by way ofline 20 at a flow rate of about 149 b./h. (10 vol. percent phenol). Thetotal amount of product (rafiinate), after solvent removal, withdrawnfrom this process was about 336 b./h.

It is to be understood that the cooler could have been used in line 13to cool the combined intermediate-raffinate stream rather than to coolonly the intermediate-rafiinate stream passing through line 34.

The yield of this example was about 73 volume percent and the efiiciencyof this process scheme was about 45.6 percent. The ratio of solvent tooil was about 1.6. The original process scheme, as shown in FIGURE 1,treated 11 lowered the operating temperature of the contacting zone 11,thus reducing the solvency of the phenol and permitting more selectiveseparation in the contacting zone 11.

It is to be understood that these examples and the accompanying drawingsare being presented for the purpose of illustration only and are notintended to limit the scope of the invention.

What is claimed is:

1. A method for increasing the efiiciency of a phenol extraction processwherein a lubricating oil distillate is treated to improve its color,ability to resist oxidation, and viscosity index and wherein saiddistillate is introduced into two parallel contacting zones havingunequal capacities, a first contacting zone and a second contactingzone, a first distillate stream is introduced into said first contactingzone and second distillate stream is introduced into said secondcontacting zone, a first phenol stream is introduced into said firstcontacting zone and is passed through said first contacting zonecountercurrently to said first distillate stream, a second phenol streamis introduced into said second contacting zone and is passed throughsaid second contacting zone countercurrently to said second distillatestream, a first rafiinate effluent and a first extract effiuent arewithdrawn from said first contacting zone, and a second efiluent and asecond extract efiluent are withdrawn from said second contacting zone,which method comprises: combining said first extract efiluent and saidsecond extract effluent to form an intermediate-extract efiiuent;passing said intermediateextract efiluent into and through anintermediate-extract surge drum; withdrawing said intermediate-extracteffluent from said intermediate-extract surge drum; dividing saidintermediate-extract eflluent into a first intermediate-extract streamand a second intermediate-extract stream; passing said firstintermediate-extract stream into and through a third contacting zone;introducing into said third contacting zone a third distillate stream,said third distillate stream being passed through said third contactingzone countercurrently to said first intermediateextract stream;withdrawing from said third contacting zone a first final-extract streamand a first intermediateratfinate stream; passing said secondintermediate-extract stream into and through a fourth contacting zone;introducing into said fourth contacting zone a fourth distillate stream,said fourth distillate stream being passed through said fourthcontacting zone countercurrently to said second intermediate-extractstream; withdrawing from said fourth contacting zone a secondfinal-extract stream and a second intermediate-raffinate stream; passingsaid second intermediate-rafiinate stream into and through anintermediate-raffinate surge drum; withdrawing said secondintermediate-rafiinate stream from said intermediateraffinate surgedrum; dividing said second intermediaterafiinate stream into a thirdintermediate-rafiinate stream and a fourth intermediate-rafiinatestream; combining said first intermediate-rafiinate stream with saidthird intermediate-raffinate stream to form a fifthintermediaterafiinate stream; passing said fifth intermediate-rafl'lnatestream into said first contacting zone, said fifthintermediate-raffinate stream being said first distillate stream that isintroduced into said first contacting zone; withdrawing as a first finalraffinate streamfrorn said first contacting zone said first raflinatethrough said second contacting zone, said fourth intermediate-raffinatestream being said second distillate stream that is introduced into saidsecond contacting zone; withdrawing as a second 8 final-rai'finatestream from said second contacting zone said second raffinate efiluent.

, 2. The method of claim 1 wherein said first contacting zone is anextraction tower and said second contacting zone is a centrifugalextractor.

3. The method of claim 2 wherein said third contacting zone and saidfourth contacting zone are of equal capacities.

4. The method of claim 3 wherein said third contact ing zone and saidfourth contacting zone are centrifugal extractors.

5. A method for increasing the capacity and the chiciency of a phenolextraction process wherein a lubricating oil distillate is treated toimprove its color, ability to resist oxidation, and viscosity index andwherein said distillate is introduced into two parallel contacting zoneshaving unequal capacities, a first contacting zone and a secondcontacting zone, a first distillate stream is introduced into said firstcontacting zone and second distillate stream is introduced into saidsecond contacting zone, a first phenol stream is introduced into saidfirst contacting zone and is passed through said first contacting zonecountercurrently to said first distillate stream, a second phenol streamis introduced into said second contacting zone and is passed throughsaid second contacting zone countercurrently to said second distillatestream, a first raffinate efiluent and a first extract effluent arewithdrawn from said first contacting zone, and a second raflinateeffluent and a second extract effiuent are withdrawn from said secondcontacting zone, which method comprises: combining said first extracteffluent and said second extract effluent to form anintermediate-extract effluent; passing said intermediate-extractefiluent into and through an intermediate-extract surge drum;withdrawing said intermediate-extract efiluent from saidintermediate-extract surge drum; dividing said intermediate-extracteffluent into a first intermediate-extract stream and a secondintermediate-extract stream; passing said first intermediate-extractstream into and through a third contacting zone; introducing into saidthird contacting zone a third distillate stream; said third distillatestream being passedthrough said third contacting zone counter: currentlyto said first intermediate-extract stream; withdrawing from said thirdcontacting zone a first finalextract stream and a firstintermediate-raflinate stream; passing said second intermediate-extractstream into and through a fourth contacting zone; introducing into saidfourth contacting zone a fourth distillate stream, said fourthdistillate stream being passed through said fourth contacting zonecountercurrently to said second intermediate-extract stream; withdrawingfrom said fourth contacting zone a second final-extract stream and asecond intermediate-rafiinate stream; passing said secondintermediate-raftinate stream into and through an intermediate-rafiinatesurge drum; withdrawing said second intermediate-raffinate stream fromsaid intermediate-raftinate surge drum; dividing said secondintermediateralfinate stream into a third intermediate-raffinate streamand a fourth intermediate-raffinate stream; cooling said firstintermediate-raffinate stream and subsequently combining said firstintermediate-raffinate stream with said third intermediate-rafiinatestream to form a fifth intermediate-raffinate stream that is about 10 F.to about 25 F. lower than the temperature of said first phenol streambeing charged to said first contacting zone; pass ing said fifthintermediate-raflinate stream into said first contacting zone, saidfifth intermediate-raffinate' stream being said first distillate streamthat is introduced into said first contacting zone; withdrawing as afirst finalraffinate stream from said first contacting zone said firstraflinate effluent; passing said fourth intermediate-rafiinate streaminto and through said second contacting zone, said fourthintermediate-rafiinate stream being said second distillate stream thatis introduced into said second contacting zone; withdrawing as a secondfinal-raffinate stream from said second contacting zone said secondrafi'lnate efiluent.

6. The method of claim wherein said first contacting zone is anextraction tower and said second contacting zone is a centrifugalextractor.

7. The method of claim 6 wherein said third contacting zone and saidfourth contacting zone are of equal capacities.

'8. The method of claim 7 wherein said third contacting zone and saidfourth contacting zone are centrifugal extractors.

9. A method for increasing the capacity and the efliciency of a phenolextraction process wherein a lubricating oil distillate is treated toimprove its color, ability to resist oxidation, and viscosity index andwherein said distillate is introduced into two parallel contacting zoneshaving unequal capacities, a first contacting zone and a secondcontacting zone, a first distillate stream is introduced into said firstcontacting zone and second distillate stream is introduced into saidsecond contacting zone, a first phenol stream is introduced into saidfirst contacting zone and is passed through said first contacting zonecountercurrently to said first distillate stream, a second phenol streamis introduced into said second contacting zone and is passed throughsaid second contacting zone countercurrently to said second distillatestream, a first raffinate efiluent and a first extract effluent arewithdrawn from said first contacting zone, and a second raflinateeffluent and a second extract effluent are withdrawn from said secondcontacting zone, which method comprises: combining said first extractefiluent and said second extract effiuent to form anintermediate-extract effluent; passing said intermediate-extracteflluent into and through an intermediate-extract surge drum;withdrawing said intermediate-extract e-flluent from saidintermediateextract surge drum; dividing said intermediate-extractefliuent into a first intermediate-extract stream and asecondintermediate-extract stream; passing said firstintermediate-extract stream into and through a third contacting zone;introducing into said third contacting zone a third distillate stream,said third distillate stream being passed through said third contactingzone countercurrently to said first intermediate-extract stream;withdrawing from said third contacting zone a first final-extract streamand a first intermediate-raifinate stream; passing said secondintermediate-extract stream into and through a fourth contacting zone;introducing into said fourth contacting zone a fourth distillate stream,said fourth distillate stream being passed through said fourthcontacting zone countercurrently to said second intermediateextractstream; withdrawing from said fourth contacting zone a secondfinal-extract stream and a secondintermediate-railinate stream; passingsaid second intermediate-raifinate stream into and through anintermediateratfinate surge drum; withdrawing said second intermediate-ratfinate stream from said intermediate-raffinate surge drum;dividing said second intermediate-rafiinate stream into a thirdintermediate-raffinate stream and a fourth intermediate-raffinatestream; combining said first intermediate-raflinate stream with saidthird intermediateraffinate stream to form a fifthintermediate-rafiinate stream; cooling said fifth intermediate-railinatestream to a temperature that is about 10 F. to about 25 F. lower thanthe temperature of said first phenol stream being charged to said firstcontacting zone; passing said fifth intermediate-raflinate stream intosaid first contacting zone, said fifth intermediate-raftinate streambeing said first distillate stream that is introduced into said firstcontacting zone; withdrawing as a first finaI-rafiinate stream from saidfirst contacting zone and said first raifinate effluent; passing saidfourth intermediate-raftinate stream into and through said secondcontacting zone, said fourth intermediate-rafiinate stream being saidsecond distillate stream that is introduced into said second contactingzone; withdrawing as a second finaI-raifinate stream from said secondcontacting zone said rafiinate effluent.

10. The method of claim 9 wherein said first contacting zone is anextraction tower and said second contacting zone is a centrifugalextractor.

11. The method of claim 10 wherein said third contacting zone and saidfourth contacting zone are of equal capacities.

12. The method of claim 11 wherein said third contacting zone and saidfourth contacting zone are centrifugal extractors.

References Cited UNITED STATES 'PATENTs 2,178,321 10/1939 Clarke 2083352,344,406 3/1944 Hibshman 208324 2,773,005 12/1956 Meyer et a1. 208-3242,846,354 8/1958 Holm et al. 208-335 HERBERT LEVINE, Primary ExaminerUS. Cl. X.R.

r Column line 8, "advantageous" should. read advantages v. ll

(5/69) UNITED STATES PATENT OFFICE CERTIFICATE. OF CORRECTEQI-I PatentNo. 3.. 5 399 Dated March 17, 1212 Inventofls) Roland L. Menzl FrederickW. Schuessleg; and Lowell 'lf jlqdds It is certified that error appearsin the above-identified patent and that said Letters Patent are herebycorrected 'as shown below:

line 33, "later" should read latter line 73, "as" should read was Column7, line 72, "contacting zone said first raffinate through said second"should read contacting zone said first raffinate effluent; passing saidfourth intermediate-raffinate stream into and through said second SIGNEDAN!) SEALED sips-197 s Amt:

Edim-d MFlew J V WILLIAM E. m.

Awning Offi er Commissioner of Patents

